The components used also impose a fairly small internal space.
A standard type of panic bolt used on panic doors has a crash bar articulated to a crash bar support.
There are two standard configuration types for articulated panic bolts: a working position and an idle position. In the idle position, the crash bar is in a position remote from the crash bar support. In the working position, which corresponds to opening the door, the crash bar is pushed toward the crash bar support when it is pushed downwardly. Returning it to the idle position necessitates return means to raise the crash bar.
In a different, push-in type of panic bolt, dedicated means are necessary to return the crash bar to a projecting position. This leads to panic bolts of the above kinds being complex and costly.